Certified Rhythm Analysis Technician (CRAT) Practice Exam

When a dual chamber pacemaker's ventricular lead senses a non-cardiac signal, it is most likely to lead to a failure to capture ventricular pace. This happens because the pacemaker may misinterpret the non-cardiac signal as a natural cardiac electrical impulse or as noise, which can interfere with its ability to deliver pacing impulses effectively to the ventricle. As a result, the device may not adequately stimulate the heart when it is supposed to, leading to a situation where the ventricle does not respond as intended to the pacing signals.

In this scenario, it's important to note that the pacemaker system is designed to respond to specific electrical signals from the heart. When it encounters noise or unintended signals, it can become confused, which impairs its function. Consequently, this disruption directly leads to the failure of properly capturing the ventricle, as the pacing impulse might not be delivered or may miss the optimal timing for effective cardiac contraction.

Other potential outcomes, such as inappropriate atrial pacing or atrial under sensing, are less likely to occur in this context, as those involve different mechanisms not primarily related to the ventricular lead sensing. Therefore, the correct answer highlights a critical aspect of pacemaker operations in response to non-cardiac